Alone with the extensive application of LED in every trade, high power LED is widely adopted as light sources in traffic, railway and electronic equipment signal lamps. As defined by its name, high power LED is provided with higher power and heat, with larger lumen than ordinary LED, thus enable it to shine brighter. Strict requirements are posed on the selection of high power LEDs used in signal lamps. Ordinary LED can not be used as signal lamps at random for the following reasons:

1. Ordinary LED generally adopts epoxy resin as the fixing board; while high power LED needs to use MCPCB.

2. Ordinary LED can use wave soldering machine or handmade soldering, while high power LED needs to use surface mount technology (SMT) soldering machine.

3. Surface mounting devices (SMD) need to be used as matched electronic devices in high power LED.

4. As high power LED adopts surface mounting technology, realizing the highly integration of its electronic devices, thus the amount of lamps board and power supply can be small. This is what ordinary LED and its matched devices can not achieve.

5. Ordinary LED bears lower power and heat, but its heat tolerance performance and heat dissipation effect is not as good as high power LED. As to high power LED, although it is comparatively concentrated, its devices are fixed on MCPCB through surface mounting technology, making the adding of radiator easily.

6. The life span of high power LED is longer and its light beams are more concentrated than those of ordinary LED.

Generally speaking, high power LED circuit has smaller amount of diodes and branches, enabling it to use power supply that provides constant current in every branch to make sure that every LED has the same power supply environment. Even when one or two LED circuit goes wrong, the current for other branches will not be influenced. Meanwhile, as the heat dissipation performance is good for high power LED, node temperature is comparatively lower than ordinary LED, enabling it to have a longer life span. Moreover, high power LED can support much larger operating current, about more than ten folds compare to ordinary one. Hence, several milliamperes’ control wave current will not do any infection on high power LED but will possibly damage ordinary LEDs, so attentions should be paid when choosing proper LEDs for signal lamps. For the above stated advantages, the application of high power LED to signal lamps is prevalent.